CN114575355A - Soil protection and descent construction method - Google Patents

Abstract

The invention relates to a soil protection and descending construction method, including S1: construction preparation; S2: construction of supporting piles; S3: construction of rotary jet piles between adjacent supporting piles; S4: construction on the top of the supporting piles Crown beam construction; S5: Retaining wall construction is carried out from the top of the foundation pit supporting pile crown beam to the ground, S6: The first anchor cable construction; S7: After the first anchor cable construction is completed, the rotary spray pile is carried out. Construction of the soil retaining wall between the first piles above; S8: Construction of the second anchor cable; S9: After the construction of the second anchor cable is completed, carry out the construction between the sprayed piles and the sprayed piles or between the sprayed piles and the supporting piles. The second soil retaining wall between piles is constructed; a relatively perfect supporting system is formed through the implementation of the supporting method of the present invention.

Description

A kind of soil protection and descending construction method

technical field

The invention belongs to the technical field of building construction, and in particular relates to a soil protection and descending construction method.

Background technique

With the rapid development of my country's economy, land resources are becoming more and more scarce, and construction projects are increasingly developing in underground spaces. For the geology of the clayey silt plain fill layer, the strata within the maximum exploration depth (45.00m) can be investigated according to the It is divided into two categories: artificial accumulation layer and Quaternary sedimentary layer, and is further divided into 7 large layers and sublayers according to the lithology and engineering characteristics of the stratum. Below the artificial accumulation layer is the Quaternary sedimentary clay silt, Sandy silt layer, silty clay, heavy silty clay layer; silt layer; silty clay, heavy silty clay layer, clay silt, sandy silt layer; clay, heavy silty clay layer and clay silt, sandy silt layer; silty clay, heavy silty clay layer and clayey silt, sandy silt layer and coarse sand layer; clay layer; The effective support of the pit will be related to the safety, quality and progress of the project construction, and the geology of the clayey silt fill layer will result in limited support forms that can be selected. It is very difficult for piles to form holes and piles during construction.

SUMMARY OF THE INVENTION

In view of this, the purpose of the present invention is to provide a kind of soil protection and descending construction method, in order to solve the clayey silt plain filling layer geology in the prior art, resulting in limited support forms that can be selected. Under geological conditions, it is a difficult technical problem when supporting piles are formed into holes and piles.

In order to achieve the above object, the technical scheme adopted by a kind of soil protection and descending construction method of the present invention is:

A soil protection and descending construction method, comprising:

S1: construction preparation;

Study the geotechnical engineering survey report of the construction area, understand the structure, distribution, performance index and groundwater distribution of the soil layer, identify various underground facilities, the spatial location, structural form, foundation depth, foundation type of the surrounding buildings, and judge The impact of the support on it is that the mechanical equipment is installed in place and operates normally, and all the required materials are in place as planned;

S2: When the construction site meets the support pile excavation conditions, the support pile construction is carried out, and the support pile pouring construction is carried out according to the design of the pile position;

S3: 48h after the construction of the supporting piles is completed, the rotary jetting pile construction is carried out between the adjacent supporting piles, and the top of the rotary jetting piles is lower than the bottom of the top of the supporting piles;

S4: After the construction of the rotary jetting pile is completed, the crown beam construction is carried out on the top of the supporting pile, and the main reinforcement of the supporting pile extends into the crown beam and is connected with the crown beam.

Rebar connection, the crown beam is supported on the top of the supporting piles and each supporting pile is connected, and the reserved steel bars are set above the crown beam;

S5: The retaining wall is constructed from the top of the crown beam of the foundation pit supporting pile to the ground. The retaining wall includes structural columns arranged at intervals, and the main bars of the structural columns are connected with the reserved steel bars of the crown beam;

S6: Construction of the first anchor cable;

S7: After the construction of the first anchor cable is completed, carry out the construction of the first soil retaining wall between the piles above the rotary jetted piles;

S8: Construction of the second anchor cable;

S9: After the construction of the second anchor cable is completed, carry out the construction of the second inter-pillar soil retaining wall between the rotary jetting pile and the rotary jetting pile or the rotary jetting pile and the supporting pile.

Beneficial effect: a soil protection and descending construction method of the present invention is through the setting of supporting piles, the construction of rotary jetting piles, the pouring construction of crown beams on the top of the supporting piles, and the building of retaining walls on the crown beams. , After the construction of the retaining wall is completed, the anchor cable construction is carried out. After the anchor cable construction is completed, the construction of the soil protection wall between the first piles above the rotary jetting pile and the rotary jetting pile and the rotary jetting pile or the rotary jetting pile and the support The construction of the second inter-pillar soil retaining wall between the piles forms a relatively complete supporting form of the foundation pit, and a relatively complete supporting system is formed through the implementation of the supporting method of the present invention, which ensures that the foundation pit has a better supporting structure. Support effect.

Further, in the construction of S2 supporting piles:

(1) First carry out the elevation measurement of the working face, the construction setting out, and determine the position of the supporting pile;

(2) Reinforcement cages are processed, and the prepared reinforcement cages are classified and stacked, and signs are used to indicate the parts of use, and they can be used only after they are qualified;

(3) Drilling into a hole;

Calculate the hole depth according to the design pile length and the elevation of the construction work surface, and mark the hole depth at the corresponding position of the drilling rig body or drill pipe;

Move the drilling rig to the pile position and align the supporting pile position, lower the drill bit, keep the tower body of the drilling rig vertical, measure the verticality of the drill pipe with theodolite or line hammer, and control the verticality deviation within 1%;

(4) Press-filled concrete;

After the drill bit reaches the design elevation, the drill pipe stops drilling and starts to pump concrete, pump the concrete to the bottom of the hole, and lift the drill while pumping the concrete. ; The pile forming process is continuously carried out until the concrete of the pile body is poured into the ground of the orifice;

(5) Reinforcement cage implantation;

After the concrete is pressed to the construction control level and the spoil around the pile hole is cleaned, the reinforcement cage is aligned with the center of the hole position for the construction of the reinforcement cage; the center of the reinforcement cage is aligned with the center of the pile position to control the verticality of the reinforcement cage; The self-weight of the rebar cage makes it sink. When the sinking stops, the vibrator is activated, and the rebar cage continues to sink through the vibrator. The height of the rebar cage is controlled by a level. After reaching the design elevation, the rebar cage is fixed.

Beneficial effects: the construction of the supporting piles is more reasonable, and the high forming quality of the supporting piles is ensured.

Further, in S3, two rotary jetting piles are set between adjacent supporting piles. After the construction of the adjacent supporting piles on both sides is completed for 48 hours, the rotary jetting piles are measured and set out, and then the rotary jetting pile machine is position, correct the hole position and the verticality of the drill pipe, carry out the drilling operation, and then put the grouting pipe in the leading hole, and perform high-pressure rotary jet grouting from bottom to top until the orifice returns to the slurry, and the position of stopping jetting is higher than the curtain. Design top lm.

Beneficial effects: the setting of the rotary jetting pile is more reasonable, the setting of the rotary jetting pile has high forming quality, and the rotary jetting pile can cooperate with the supporting pile to form a supporting foundation with strong peripheral structure of the foundation pit.

Further, in the construction of S4 crown beam:

(1) Chisel pile head and clear soil;

Chisel off the floating slurry on the top of the supporting pile and the mixed soil of the redundant pile body, remove the residual concrete on the main reinforcement of the supporting pile, ensure that the length of the main reinforcement of the supporting pile extending into the crown beam meets the design requirements, and overlap the main reinforcement with the reinforcement of the crown beam welding;

(2) Carry out the crown beam formwork; carry out the crown beam formwork between the supporting piles, and clean the contact surface between the formwork and the concrete and apply the release agent after the formwork is completed;

(3) Concrete pouring and curing;

The crown beam concrete is continuously poured, and the concrete is covered within 12 hours after the concrete is poured, and the heat preservation and curing time of the concrete is more than or equal to 7 days.

Beneficial effects: the crown beams are arranged at the top of the supporting piles to form a connection, so that each supporting pile is connected at the top, so that the supporting piles and the crown beams form a stable supporting foundation.

Further, in the construction of the S5 retaining wall: the retaining wall is built in layers, and the concrete strength of the structural column of the retaining wall reaches 70% of the design strength before backfilling.

Beneficial effects: ensure that the retaining wall has high structural stability.

During the construction of the soil retaining wall between the first piles of S7:

(1) For the construction of the soil retaining wall between the first piles, drill holes on the opposite side of the supporting piles. The drilled holes are set perpendicular to the extension direction of the supporting piles. The limit rod is fixed on the top of the rotary jet pile correspondingly. The vertical limit rod and the horizontal limit rod are welded and connected to form a limit net, and then the steel mesh is laid on the side of the limit steel that faces away from the foundation pit. ;

(2) Surface spray coagulation;

The spraying operation should be carried out in sections from top to bottom, and the spraying sequence of the same section should be from bottom to top; when spraying, the nozzle and the sprayed surface should be kept vertical, and the spraying distance should be 0.6~1.0m. Fine stone concrete with a thickness of 80mm and a strength of C20 is sprayed.

Beneficial effect: The dense first inter-pile soil retaining wall structure is formed under the crown beam, which not only ensures that the first inter-pile soil retaining wall structure can support the side walls of the foundation pit relatively well, but also ensures that the retaining wall has a higher level of protection. Support strength.

In the construction of the soil retaining wall between the second piles of S9:

(1) During the construction of the soil retaining wall between the second piles, drill holes on the opposite side of the supporting piles and the jetting piles or on the opposite side of the jetting piles and the jetting piles. Lap welding to form a lateral limit rod, and then lay the reinforcing mesh on the side of the limit steel facing away from the foundation pit;

(2) Surface spray coagulation;

The spraying operation should be carried out in sections from top to bottom, and the spraying sequence of the same section should be from bottom to top; when spraying, the nozzle and the sprayed surface should be kept vertical, and the spraying distance should be 0.6-1.0m. Fine stone concrete with a thickness of 80mm and a strength of C20 is sprayed.

Beneficial effect: A dense second inter-pile soil retaining wall structure is formed under the crown beam, which not only ensures that the second inter-pile soil retaining wall structure can better support the sidewall of the foundation pit, but also ensures that the retaining wall has a high Support strength.

Before the construction of the supporting piles, excavate the earthwork 20m away from the supporting piles, excavate from the inside to the outside, and carry out 1:1 grading, so that the supporting piles meet the excavation conditions.

Beneficial effects: The earthwork excavation carried out before the construction of the support piles ensures that the support piles meet the excavation conditions.

Description of drawings

Fig. 1 is the construction flow chart of a kind of soil protection and descending construction method of the present invention;

2 is a side view of a supporting structure formed by a soil protection and descending construction method of the present invention;

FIG. 3 is a front view of the support structure formed by the soil protection and descending construction method of FIG. 2 .

Reference signs: 1-supporting pile; 2-spraying pile; 3-crown beam; 4-retaining wall; 5-anchor cable; 6-soil protection wall between the first piles; 7-soil protection wall between the second piles; 8- horizontal limit rod; 9- vertical limit rod; 10- steel mesh; 11- structural column; 12- transverse pressure bar.

Detailed ways

A kind of soil protection and descending construction method of the present invention is described in further detail below in conjunction with the accompanying drawings and specific embodiments:=

As shown in Figure 1, the soil protection and descending construction method of the present invention comprises:

S1: construction preparation;

Study the geotechnical engineering survey report of the construction area, understand the structure, distribution, performance index and groundwater distribution of the soil layer, identify various underground facilities, the spatial location, structural form, foundation depth, foundation type of the surrounding buildings, and judge The support is affected, the mechanical equipment is installed in place and operates normally, and all the required materials are in place as planned.

The natural dynamic type of platform diving in the project site is infiltration-flow and evaporation type, which is mainly recharged by groundwater lateral flow, atmospheric precipitation infiltration and pipeline leakage, and groundwater lateral flow and evaporation are the main discharge methods; The annual dynamic variation of the water level is generally as follows: the water level is relatively high from June to September, and the water level in other months is relatively low. The annual variation of the water level is generally about 1.0 to 2.0 m.

The main purpose of the foundation pit dewatering is to control the groundwater below the excavation depth of the foundation pit, so as to ensure the earthwork excavation and structural dry groove operations.

The groundwater control of the foundation pit is treated by the scheme of water-stop curtain + dredging in the pit. The foundation pit adopts the high-pressure rotary jet pile 2 water-stop curtain to stop the water, the pile diameter is 700mm, the spacing is 500mm, and the pile length is 13.2m; The dry well is used to drain the groundwater inside the foundation pit. The drain well is a tube well with a diameter of φ600, a spacing of 20.0m × 20.0m, and a well depth of 17.0m. The well tube is a cement gravel water filter tube with a diameter of 400mm; the outside of the well tube is filled with 2-10mm Gravel filter media.

S2: When the construction site meets the support pile excavation conditions, the support pile construction is carried out, and the support pile pouring construction is carried out according to the design of the pile position. In the construction of S2 supporting piles:

Before the construction of supporting pile 1, excavate the first layer of earthwork 20m away from the supporting pile, that is, excavate the first layer of earthwork around the foundation pit, excavate from the inside to the outside, and carry out a 1:1 excavation. Slope, so that the supporting pile 1 can meet the construction conditions and the construction site can meet the requirements of safe walking of pile drivers and tankers. After the supporting pile 1 meets the construction conditions, the construction shall be carried out according to the following steps:

As shown in Figure 2 and Figure 3:

(1) First, carry out the elevation measurement of the working face, and set out the construction line, and determine the 1st position of the supporting pile.

Before the construction of the support pile 1, measure the elevation of the construction work surface, and calculate the drilling depth from the construction work surface.

The positioning mark of the supporting pile 1 should be reliable and stable, and the deviation of the pile position should not be greater than 70mm. After the line is laid out, the line will be inspected together with the supervisor, and the next process can be carried out only after confirming that it is correct and signing for approval.

(2) Reinforcement cages are processed, and the prepared reinforcement cages are classified and stacked, and the use part is marked with a signboard, and it can be used only after the acceptance is qualified.

(3) Drilling into a hole;

Calculate the hole depth according to the design pile length and the elevation of the construction work surface, and mark the hole depth at the corresponding position of the drilling rig body or drill pipe;

Move the drilling rig to the pile position, align the supporting pile 1, and lower the drill bit. The tower body of the drilling rig is kept vertical. Use the theodolite or line hammer to measure the verticality of the drill pipe, and the verticality deviation is controlled within 1%.

(4) Press-filled concrete;

After the drill bit reaches the design elevation, the drill pipe stops drilling and starts to pump concrete, pump the concrete to the bottom of the hole, and lift the drill while pumping the concrete. ; The pile forming process is continued until the concrete of the pile body is poured to the ground of the orifice.

(5) Reinforcement cage implantation;

After the concrete is pressed to the construction control level and the spoil around the pile hole is cleaned, the reinforcement cage is aligned with the center of the hole position for the construction of the reinforcement cage; the center of the reinforcement cage is aligned with the center of the pile position to control the verticality of the reinforcement cage; The self-weight of the rebar cage makes it sink. When the sinking stops, the vibrator is activated, and the rebar cage continues to sink through the vibrator. Use a level to control the height of the rebar cage. After reaching the design elevation, fix the rebar cage.

The formed supporting pile 1 has a pile diameter of 800mm, a pile length of 18m, and a pile spacing of 1.5m.

S3: 48 hours after the completion of the construction of the supporting pile 1, the construction of the rotary jetting pile 2 is carried out between the adjacent supporting piles 1, and the top of the rotary jetting pile 2 is lower than the bottom of the top of the supporting pile 1.

Two rotary jetting piles 2 are set between adjacent supporting piles 1. After the construction of the adjacent supporting piles 1 on both sides is completed for 48 hours, the rotary jetting pile 2 is measured and set out, and then the rotary jetting pile machine is in place to calibrate The hole position and the verticality of the drill pipe, carry out the drilling operation, and then put the grouting pipe in the leading hole, and perform high-pressure rotary jet grouting from bottom to top until the orifice returns to the slurry, and the position where the jet stops is higher than the top surface of the curtain design lm.

Rotary spray pile 2 has a pile diameter of 700mm, a pile length of 13.2m, and a spacing of 0.5m.

Curtain pile plugging methods include:

(1) The seepage between the piles can be blocked by the "support form plugging method" method. The method is as follows:

16@200单层钢筋网片，渗漏点高度3m以下的采用木模板在外侧进行单侧支模。漏点高度大于3m的采用喷射C20细石混凝土封堵，混凝土强度达到要求后将模板拆除。Drill holes and plant steel bars on the piles at the outer position of the center of the supporting pile 1, and set up between the piles.

16@200 single-layer reinforced mesh, the leakage point height is less than 3m, and the wooden formwork is used for single-side formwork on the outside. If the leak height is greater than 3m, use the sprayed C20 fine stone concrete to block, and remove the formwork after the concrete strength meets the requirements.

(2) When the water-stop curtain is leaking but the amount of water leakage is not large and a small amount of mud and sand is entrained, the method of "internal plugging" can be used for plugging, and the method is as follows:

1) Leakage point treatment: remove the soil and impurities between the enclosure piles at the leaking site, chisel the leakage area into an inverse wedge-shaped hole, chisel both sides to the side of the enclosure pile, and clean the soil on the surface of the enclosure pile.

2) Mixing cement: "Double quick-setting cement" must be used for quick plugging. The cement and water are repeatedly kneaded into a ball at a ratio of 1:0.2. When sealing, press cement:water=1:0.3 to stir into a uniform putty-like shape. , the initial setting time of double-fast cement is 0.2h, and the final setting time is 1.5h.

3) Insert filler: If there is a lot of sediment loss in the gap and there are large holes inside, put old cotton wool or rags into the holes. The old cotton wool or rags can not only prevent the loss of sediment and prevent the holes from expanding, but also Water permeable.

4) Insert the catheter: spread the mixed cement in a layer at the bottom of the wedge-shaped hole, the thickness is about one-third of the hole, and quickly put the prepared Φ25 plastic pipe with a length of about 1.5m (pipe diameter according to the leak point) Water flow adjustment) insert one end into the depth of the leaking point, press the water pipe into the tiled cement, confirm that the water flow at the leaking point flows away from the pipe and continue to lay the mixed cement fixed aqueduct.

5) Seal the leaking hole: quickly plug the mixed cement mass into the water seepage opening, and seal the surrounding of the inserted aqueduct with cement mass. After confirming that all the leaking water is discharged by the aqueduct and no longer seeping into other parts, extend a range of 10cm around the hole and then scrape a layer. After the pipe is fixed, insert a filter at the end of the pipe to filter the sediment to ensure that only water flows in the pipe and does not take away the sediment.

6) Maintenance: maintenance is not less than 4 hours, such as hot weather, appropriate water spray maintenance.

7) Tie the pipe to stop the water: After the cement hardens to meet the strength (above 20MPa) requirements, tie the plastic aqueduct with lead wire to stop the water. Sometimes due to the high water pressure, the water may leak out from other parts after tying the pipe, and re-drain and block it according to the above method until it is blocked.

(3) When the water-stop curtain is leaking and the amount of water leakage is large and the sediment is entrained, the method of "outer sealing" must be used for sealing. The specific methods are as follows:

1) Find the source of water leakage on the inside of the foundation pit, clean the inside of the leakage point and the surrounding of the hole, and dig the leakage point into a type with large inside and outside during excavation, so as to facilitate the installation of expanding materials such as dried kelp, and at the same time fill with cotton wool to reduce water leakage Carry mud.

2) Backfill as cofferdam: quickly backfill soil for leakage as cofferdam, and pour concrete as cofferdam in case of serious water leakage to reduce the damage to foundation pit caused by water leakage.

3) Drilling into a hole: use a truck crane to place the drilling rig at the leaking point, adjust the verticality and start drilling, and the drilling depth is 1m below the leaking point.

4) Placing the grouting pipe: after drilling to the depth, lift the drill pipe and place the grouting pipe (φ25 galvanized pipe). If the sand layer is encountered during the process of placing the grouting pipe and the borehole collapses, use a modified plate vibrator. The grouting pipe is pressed into a predetermined depth, and a tee with two valves is connected to the grouting pipe, which are respectively used to connect the cement grouting pump and the water glass grouting pump.

5) Cement grouting: Mix the cement slurry according to the water-cement ratio of 0.7:1, and inject the cement slurry first to confirm whether the grouting pipe is near the leaking channel. ~20cm, the leaking channel can only be confirmed after the cement slurry flows out of the leaking point.

6) Two-liquid grouting: Two-liquid grouting is a kind of static pressure grouting, that is, using hydraulic pressure to mix cement solution and water glass evenly in a short time through a grouting pipe to form cement glue, and then inject it into the formation. Using the characteristics of fast setting speed and fast strength improvement of cement glue, the leakage channel is blocked to achieve the purpose of plugging.

7) Grouting reinforcement

①Hydrostatic grouting: 24 hours after the water leakage point is blocked, static pressure grouting is used for reinforcement. The reinforcement points are arranged along the direction of the water-stop curtain, and a reinforcement point is set at a distance of 0.5m to the left and right of the leakage point. The grouting depth is 1m below the leakage point. The flow rate is 8~12L/min, and the grouting pressure is above 1~1.5MPa during reinforcement.

②Split grouting: When the hydrostatic grouting is used for reinforcement, due to the large density of the lower soil layer, the slurry is not easy to spread, and the pores between the grouting pipe and the borehole are large, and the grouting is serious during grouting. Therefore, split grouting is used. During the drilling process, the clay powder slurry is injected to lubricate the drill pipe, prevent the hole from being blocked, and reduce the resistance when the split grouting pipe is placed. , 2 days later, insert the grouting flower tube into the split tube, and perform grouting in layers (50cm), and the grouting pressure is 2MPa until it is full and returns to the grouting.

S4: After the construction of the rotary jetting pile 2 is completed, the crown beam construction is carried out on the top of the supporting pile 1. The main reinforcement of the supporting pile 1 extends into the crown beam 3 and is connected with the reinforcement of the crown beam 3, and the crown beam 3 is supported on the supporting pile 1. At the top, each supporting pile 1 is connected, and reserved steel bars are arranged above the crown beam 3 .

Specifically, including:

(1) Chisel pile head and clear soil;

Chisel off the floating slurry on the top of the supporting pile 1 and the excess pile body mixed with simulated soil, remove the residual concrete on the main reinforcement of the supporting pile 1, ensure that the length of the main reinforcement of the supporting pile 1 into the crown beam 3 meets the design requirements, and connect the main reinforcement and the crown beam. 3 The steel bars are lap welded.

(2) Carry out three forms of crown and beam; carry out three forms of crown and beam between supporting piles 1, and clean the contact surface of formwork and concrete and apply release agent after the end of form support.

(3) Concrete pouring and curing.

The crown beam 3 concrete is continuously poured, and the concrete is covered and maintained within 12 hours after the completion of the concrete pouring.

S5: The retaining wall 4 is constructed in the range from the top of the crown beam 3 of the foundation pit supporting pile 1 to the ground.

The retaining wall 4 is built in layers, and the concrete strength of the structural column 11 of the retaining wall 4 reaches 70% of the design strength before backfilling.

During the construction of the supporting pile 1, the construction of the rotary jetting pile 2, the construction of the crown beam 3, and the construction of the retaining wall 4, the center earth excavation of the first layer of the foundation pit is carried out. When the construction of the retaining wall 4 is completed and the excavation of the first layer of central earthwork is completed, the construction of the dredging well and the dewatering in the central area of the foundation pit are carried out. This will not be repeated here.

S6: Construction of the first anchor cable 5;

Before the construction of the first anchor cable 5, earthwork excavation is carried out around the second layer, and then the first anchor rod construction is carried out.

During the construction of the first anchor cable 5, the following steps are included:

(1) Hole forming, the construction of the anchor cable 5 adopts the casing follow-up hole forming process, and the casing follow-up hole forming process is the prior art, which will not be repeated here.

(2) The rod body is made. The anchor rod body is made of 1860 grade Ф15.20 steel strand. The length of the rod body should be about 1.0m longer than the length of the tunnel.

(3) When the rod is placed, the excavation speed should be coordinated with the construction speed of the prestressed anchor cable 5. The soil should be cleared to 500mm below the elevation of the prestressed anchor cable 5. Over-excavation is strictly prohibited.

(4) For grouting, the anchor cable 5 must adopt a secondary high-pressure split grouting process, the pressure for termination of grouting should not be less than 1.5MPa, the cement consumption in the anchoring section should not be less than 60kg/m, and the strength of the cement slurry should be M20. The second high pressure split grouting is carried out 12-24 hours after the first grouting (the specific interval is controlled by the anchor strength reaching about 5MPa). The secondary high-pressure splitting grouting pipe shall have an overflow hole in the anchoring section, and the spacing of the overflow hole shall be an overflow hole every 1.0m in the 1/3 section at the end of the anchoring section. Seal the bottom port and opening with waterproof tape to prevent the grouting pipe from entering the grout during the first grouting, resulting in the failure of the second high-pressure split grouting.

(5) The waist beam processing and installation, the anchor cable 5 waist beams between the supporting piles 1 piles are 2×I28b I-beams. The two I-beams are connected by slats, and the spacing is the same as that of the supporting pile 1.

After the construction of the anchor cable 5 is completed, it is tensioned and locked.

S7: After the construction of the first anchor cable 5 is completed, the construction of the first inter-pile soil retaining wall 6 located above the rotary jetted pile 2 is carried out. The first inter-pile soil retaining wall 6 is shown in FIG. 3 .

(1) For the construction of the soil retaining wall 6 between the first piles, drill holes on the opposite side of the supporting piles 1. The drilled holes are set perpendicular to the extension direction of the supporting piles 1, and two sections of transverse pressure bars 12 are inserted into the drilled holes and then erected. The horizontal limit rod 8 is formed by welding, and the vertical limit rod 9 is correspondingly fixed on the top of the rotary jet pile 2. The vertical limit rod 9 is fixed between the rotary jet pile 2 and the crown beam 3 in the up and down direction. The rod 9 is welded and connected with the lateral limit rod 8 to form a limit net, and then the reinforcing mesh 10 is laid on the side of the limit steel facing away from the foundation pit.

(2) Surface spray coagulation;

The spraying operation should be carried out in sections from top to bottom, and the spraying sequence of the same section should be from bottom to top; when spraying, the nozzle and the sprayed surface should be kept vertical, and the spraying distance should be 0.6-1.0m. Fine stone concrete with a thickness of 80mm and a strength of C20 is sprayed.

S8: Construction of the second anchor cable 5.

The second anchor cable 5 is located directly below the first anchor cable 5. Before the construction of the second anchor cable 5, earthwork excavation around the third layer is carried out, and at the same time, the center earthwork excavation of the second layer is carried out, and the surrounding area is dredged. construction and precipitation. The construction steps of the second anchor cable 5 are the same as the construction steps of the first anchor cable, and are not repeated here.

S9: After the construction of the second anchor cable 5 is completed, the construction of the second inter-pillar soil retaining wall 7 between the rotary jetting pile 2 and the rotary jetting pile 2 or the rotary jetting pile 2 and the supporting pile 1 is carried out, and the soil between the second piles is constructed. The protective wall 7 is shown in FIG. 3 .

(1) During the construction of the soil retaining wall 7 between the second piles, drill holes on the opposite side of the supporting pile 1 and the spraying pile 2 or on the side opposite the spraying pile 2 and the spraying pile 2, and pierce the two sections of transverse reinforcement bars. 12 is inserted into the drilled hole and then overlapped and welded to form the lateral limit rod 8, and then the reinforcing mesh 10 is laid on the side of the lateral limit rod 8 facing away from the foundation pit.

(2) sprayed concrete for the surface layer;

The spraying operation should be carried out in sections from top to bottom, and the spraying sequence of the same section should be from bottom to top; when spraying, the nozzle and the sprayed surface should be kept vertical, and the spraying distance should be 0.6-1.0m. Fine stone concrete with a thickness of 80mm and a strength of C20 is sprayed.

If the third anchor cable construction needs to be carried out, continue to carry out the earthwork excavation around the fourth layer, then continue to carry out the third anchor cable construction, and the soil retaining wall construction, in turn, until the depth of the soil retaining wall reaches the design depth of the foundation pit.

In the above-mentioned embodiments, two jetting piles are arranged between adjacent supporting piles, and in other embodiments, one jetting jetting pile is arranged between adjacent supporting piles.

In the above-mentioned embodiment, before carrying out the construction of the supporting piles, excavate the earthwork 20m away from the supporting piles, excavate from the inside to the outside, and conduct 1:1 grading, so that the supporting piles meet the excavation conditions; other In the embodiment, if the site satisfies the construction conditions of the support piles before the construction of the support piles, the construction of the support piles can be directly carried out.

Claims (8)

1. A soil-protecting and descending construction method is characterized by comprising the following steps:

s1: construction preparation;

researching a geotechnical engineering investigation report of a construction area, knowing the structure, distribution, performance indexes and underground water distribution condition of a soil layer, finding out the spatial position, structural form, foundation burial depth and foundation type of various underground facilities and surrounding buildings, judging the influence of support on the underground facilities and the surrounding buildings, installing mechanical equipment in place and operating normally, and putting all required materials in place according to a plan;

s2: when a construction site meets the excavation condition of the supporting piles, carrying out supporting pile construction, and installing design pile positions to carry out supporting pile pouring construction;

s3, after the construction of the supporting piles is finished for 48 hours, carrying out the construction of the jet grouting piles between the adjacent supporting piles, wherein the top of each jet grouting pile is lower than the lower part of the top of each supporting pile;

s4: after the construction of the jet grouting pile is completed, the top of the supporting pile is constructed with a top beam, and the main reinforcement of the supporting pile extends into the top beam and is connected with the top beam

Connecting steel bars, wherein a crown beam is supported at the top of the support piles and connects the support piles, and a reserved steel bar is arranged above the crown beam;

s5: constructing a retaining wall in the range from the top of a crown beam of the supporting pile of the foundation pit to the ground, wherein the retaining wall comprises constructional columns arranged at intervals, and main reinforcements of the constructional columns are connected with reserved reinforcing steel bars of the crown beam;

s6: constructing a first anchor cable;

s7: after the first anchor cable construction is finished, performing first inter-pile soil retaining wall construction above the jet grouting pile;

s8: constructing a second anchor cable;

s9: and after the second anchor cable is constructed, performing second inter-pile soil retaining wall construction between the jet grouting pile and the jet grouting pile or between the jet grouting pile and the support pile.

2. A soil lifting construction method according to claim 1, wherein in the construction of S2 fender piles:

(1) firstly, carrying out height measurement and construction setting-out on an operation surface, and determining a supporting pile site;

(2) processing the reinforcement cage, stacking the manufactured reinforcement cage in a classified manner, marking the use part by using a signboard, and using the reinforcement cage behind an experience folding lattice;

(3) drilling to form a hole;

calculating the hole depth according to the designed pile length and the elevation of the construction working surface, and marking the hole depth at the corresponding position of the body or the drill rod of the drilling machine;

the drilling machine moves to a pile site to align with a pile site of a support pile and lower a drill bit, the tower body of the drilling machine is kept vertical, the verticality of a drill rod is measured by a theodolite or a plumb bob, and the verticality deviation is controlled within 1%;

(4) pressure pouring concrete;

after the drill bit reaches the designed elevation, the drill rod stops drilling and starts to pump concrete, the concrete is pumped to the bottom of the hole, the drill is lifted while the concrete is pumped, the drill lifting speed is matched with the pumping quantity, and the drill bit is guaranteed to be buried below the concrete surface all the time; the pile-forming process is continuously carried out until the pile body concrete is poured to the ground of the hole opening;

(5) implanting a reinforcement cage;

after the concrete is pressure-poured to a construction control elevation and waste soil around the pile hole is cleaned, aligning the reinforcement cage to the center of the hole position to carry out reinforcement cage implantation construction; aligning the center of the reinforcement cage to the center of the pile position, and controlling the verticality of the reinforcement cage; make it sink through the steel reinforcement cage dead weight earlier, when sinking and stopping, start the electromagnetic shaker, make the steel reinforcement cage continue to sink through the electromagnetic shaker, height that the steel reinforcement cage was placed is controlled to the levelling instrument, after reacing the design elevation, fixed steel reinforcement cage.

3. A soil protection and descent construction method as claimed in claim 2, wherein in S3, two jet grouting piles are arranged between adjacent supporting piles, after the construction of the supporting piles adjacent to both sides is completed for 48 hours, the jet grouting piles are measured and paid out, then the jet grouting piles are put in place, the hole site and the drill rod verticality are corrected, the hole leading operation is performed, then grouting pipes are arranged in the holes, high-pressure jet grouting is performed from bottom to top until the hole orifice returns, and the position where the jet stopping is higher than the curtain design top surface lm.

4. A soil drop construction method as claimed in claim 3, wherein in S4 crown beam construction:

(1) drilling a pile head and clearing soil;

chiseling floating slurry on the top of the supporting pile and excess pile body mixed soil, removing residual concrete on a main reinforcement of the supporting pile, ensuring that the length of the main reinforcement of the supporting pile extending into the crown beam meets the design requirement, and lap-welding the main reinforcement and the crown beam steel bar;

(2) performing crown beam formwork support; performing crown beam formwork support between the support piles, cleaning the contact surface of the formwork and the concrete after the formwork support is finished, and coating a separant;

(3) pouring and maintaining concrete;

and (3) continuously pouring the crown beam concrete, covering the concrete within 12 hours after the concrete is poured, and maintaining the concrete in a heat-preservation way for more than or equal to 7 days.

5. A soil drop construction method according to claim 4, wherein in the construction of the S5 retaining wall: and (4) building the retaining wall in layers, and backfilling after the concrete strength of the constructional columns of the retaining wall reaches 70% of the design strength.

6. A soil lifting construction method according to any one of claims 1 to 4, wherein in the first inter-pile soil retaining wall construction of S7:

(1) the construction method comprises the steps of constructing a first inter-pile soil retaining wall, drilling a hole in one opposite side of a support pile, wherein the drilled hole is perpendicular to the extending direction of the support pile, inserting two sections of transverse pressing bars into the drilled hole, then overlapping and welding to form a transverse limiting rod, correspondingly fixing a vertical limiting rod on the top of a jet grouting pile, welding and connecting the vertical limiting rod and the transverse limiting rod to form a limiting net, and then laying a reinforcing mesh on one surface of the limiting steel, which is back to a foundation pit;

(2) spraying and coagulating a surface layer;

the spraying operation is performed from top to bottom in sections, and the spraying sequence of the same section is from bottom to top; when in spraying, the spray head and the sprayed surface are kept vertical, and the spraying distance is 0.6-1.0 m;

spraying the fine stone concrete with the thickness of 80mm and the strength of C20.

7. The soil lifting construction method of claim 6, wherein in the second inter-pile soil retaining wall construction of S9:

(1) during construction of the soil retaining wall between the second piles, drilling holes in one side of the support pile opposite to the rotary jet grouting pile or one side of the rotary jet grouting pile opposite to the rotary jet grouting pile, inserting two sections of transverse pressing bars into the drilled holes, then overlapping and welding the transverse pressing bars to form transverse limiting rods, and then paving a reinforcing mesh on one surface of the limiting steel, which faces away from the foundation pit;

(2) spraying and coagulating the surface layer;

the spraying operation is performed from top to bottom in a segmented mode, and the spraying sequence of the same segment is from bottom to top; when spraying, the spray head and the sprayed surface should be kept vertical, and the spraying distance is 0.6-1.0 m;

spraying the fine stone concrete with the thickness of 80mm and the strength of C20.

8. A method of civil engineering works as claimed in any of claims 1 to 4 wherein, before the construction of the supporting piles, earth excavation is carried out at a distance of 20m from the supporting piles, excavation is carried out from the inside to the outside, and 1: 1, slope releasing so that the supporting piles meet excavation conditions.

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